Lanes v. Montana State Fund, 2008 MT 306, 346 Mont. 10, 192 P.3d 1145The aggravation provision is a reflection of the long-standing rule that employers take their workers as they find them and that a traumatic event or unusual strain which lights up, accelerates, or aggravates an underlying condition is compensable. However, case law has established that an aggravation must be “significant” before it will be considered the last injurious exposure. Where Petitioner and his treating physician both testified that his job duties as a minister only temporarily aggravated his pre-existing knee condition, this does not constitute the last injurious exposure.

[1999]Montana
State Fund v. Murray, 2005
MT 97 (No. 04-576) Where claimant alleges an occupational exposure
worsened a preexisting condition and led to benefit entitlement, the
test for compensability under the Occupational Disease Act is whether
occupational factors significantly aggravated the preexisting condition,
not whether there was a “substantial” aggravation.

[1993]Polk
v. Planet Insurance Co., 287 Mont. 79, 951 P.2d 1015 (1997) In
light of the occupational disease proximate cause requirement, set out
at section 39-71-408, MCA, and the aggravation statute, section 39-71-706,
MCA, occupational aggravations of preexisting non-occupational diseases
are compensable, as are occupational diseases which are aggravated by
non-occupational factors. The test for compensability under the OD Act
is whether occupational factors significantly aggravated a preexisting
condition, not whether occupational factors played the major or most significant
role in causing a particular disease. As long as an occupational exposure
substantially aggravated a pulmonary condition, claimant is entitled to
pro rata compensation for his disease. The DOL hearing examiner, and the
WC Court, erred in basing their decision on medical opinions by physicians
who operated under the mistaken assumption that occupational irritants
had to be the major factor causing a pulmonary condition for claimant
to receive compensation.

[1995]Baumgartner
v. Liberty NW [4/14/97] 1997 MTWCC 19 Although it would take little
more than three years for occupational disease claimant's wage loss to
reach $10,000, meaning he would ordinarily qualify for the maximum indemnity
award under section 39-72-405, MCA (1995), the Court applied the apportionment
provisions of section 39-72-706, MCA (1995) to an award under section
405. Where medical evidence attributed only 60% of the causation of claimant's
low back condition to work, he was awarded $6,000.